The present invention relates generally to automatic decapsulators and more particularly to the device protection unit utilized in such decapsulators.
Automatic decapsulators are used to expose the die in any plastic package or device by etching away the die""s plastic covering. Either fuming sulfuric, fuming nitric, or mixed fuming nitric and sulfuric acids may be used as an etchant. Decapsulation is a fast and safe process that produces a clean, uncorroded die surface. When fuming nitric acid is used as the etchant, there is little or no damage to the die surface or bond pads. Fuming sulfuric acid is normally used at an elevated temperature to remove the plastics that are not compatible with fuming nitric acid. The etching process is performed under pressure in an inert atmosphere to reduce metal oxidation and to reduce the production of harmful fumes.
FIG. 1a illustrates a side view of a typical system for automatic decapsulation of a device. The system 10 includes a safety cover 11 which is coupled to an etch plate 13. The system 10 also includes a positioning fixture 12 coupled to the etch plate 13 which is typically metal and is aligned with a package 16 and a gasket 14, typically made of rubber. The gasket 14 is positioned under the device 16 with an etch window in the gasket""s center. During decapsulation, the device holder 20 presses down on the device 16, which presses down upon the rubber gasket 14, creating a tight seal with the etch head 18. The etchant is then provided by the etch head 18 through the etch window to the device 16.
For many current plastic packages, such as plastic ball grid array (PBGA) or fine ball grid array (FBGA) packages, solder balls are disposed on the backside of the package, i.e., on the face opposite to that exposed to the etchant. Decapsulating such packages is a challenge because the decapsulation temperature exceeds the melting point of the solder balls, and the solder balls can be deformed by the device holder. Moreover, some packages, like FBGA packages, can be as small as 5 mm on each side, thereby presenting alignment problems.
Co-pending U.S. patent application Ser. No. 09/680,558 entitled, xe2x80x9cAutomatic Decapsulation System Utilizing An Acid Resistant, High Heat Endurance and Flexible Sheet Coupled to a Rubber Gasket and Method of Use,xe2x80x9d filed on Oct. 5, 2000, and assigned to the assignee of the present invention, addresses some of the challenges faced when decapsulating ball grid array packages. According to one embodiment of the co-pending patent application, a spacer and a protection plate are disposed between the device and the device holder so that the device holder does not come in direct contact with the backside of the device. The spacer makes contact with the backside of the device only in areas without solder balls. Accordingly, the spacer prevents the protection plate from deforming the solder balls during decapsulation.
FIG. 2a illustrates a side view of the automatic decapsulation system 100 in accordance with the above-referenced co-pending application. The system 100 is similar to the system 10 of FIG. 1, and includes a safety cover 11xe2x80x2 which is coupled to an etch plate 13xe2x80x2. As is seen, a spacer 108 is inserted between the backside of the package 110 and the protection plate 106. A rubber gasket 104 is placed between a gasket plate 102 and a head etch 18xe2x80x2. The spacer 108 is preferably made of a TEFLON sheet having a thickness of at least the height of the solder balls. TEFLON(copyright) is well known in the art. The generic term for TEFLON is polytetrafluoroethylene (PTFE). FIG. 2b illustrates a top view of the backside of the device 110 with the spacer 108 in accordance with the present embodiment. As is shown, a window is cut out of a sheet (not shown) to form the spacer 108, which surrounds and protects the solder balls. Accordingly, when the protection plate 106 is placed on top of the spacer 108, the plate 106 does not come in contact with the backside of the device 110, and the solder balls are protected from being crushed.
Although the above-described system in the co-pending patent application functions for its intended purpose, one of ordinary skill in the art will readily recognize that it would be desirable to improve the way in which the backside of the device is protected. For instance, it would be desirable to simplify the placement of the spacer, such that alignment with a very small device, such as a FBGA package, is accomplished with relative ease. It also would be desirable to devise a system in which the protection plate is easily put in place and kept in place during decapsulation. In addition, it would be desirable to reduce the cost and labor associated with manufacturing different spacers having different sizes to match the various package sizes.
Accordingly, what is needed is a system and method to overcome the above-identified problems. The system and method should be cost effective and easy to implement with existing processes and equipment. The present invention addresses such a need.
An automatic decapsulation system for a device is disclosed. The system comprises an etch plate, an etch head, a sheet coupled to the etch head, a rubber gasket disposed between the etch head and the sheet, and an integrated spacer and protection plate for securing the device without damaging the backside of the device during decapsulation. In one embodiment of the present invention, the integrated spacer and protection plate is adjustable to accommodate devices of varying sizes.
The integrated spacer and protection plate of the present invention automatically aligns the spacer with the device, thereby reducing the amount of time taken to otherwise align the spacer. In addition, because the spacer and protection plate are integrated, the protection plate is put in place and kept in place automatically. In a preferred embodiment, the integrated spacer and protection plate is manufactured from a TEFLON sheet, thereby providing a highly durable and cost efficient solution.